1. Field of the Invention
This invention relates to a reel for winding a traveling, substantially continuous web. More particularly, this invention relates to a reel for winding the paper sheet produced on a papermaking machine. Still more particularly, this invention relates to an improved Pope-type reel on a papermaking machine. Such a reel incorporates a driven support drum about which a pair of primary arms are co-axially mounted. The primary arms accept a reel spool, bring it into engagement with the support drum at a location about the upper periphery thereof, and rotate the reel spool about the support drum and deposit it onto a pair of horizontally disposed guide rails. The paper sheet begins to be wound about the reel spool at its location about the upper periphery of the support drum and is wound into a partial wound paper roll by the time the reel spool is deposited onto the guide rails.
2. Description of the Prior Art
Wound paper rolls must be structured properly to avoid inducing web defects during the winding process. The so-called Pope-type reels, while mechanically effective, tend to produce wound rolls of paper where the paper wound near the reel spool, such as from about 5 cm to about 15 cm from the reel spool surface, is defective, such as by having so-called core bursts, wrinkles, tears or other defects generally related to excessive compression during the winding process. It is imperative that the initial web wraps on the core, or reel spool, are tight enough to avoid layer-to-layer slippage and bursting. However, the paper web cannot be wrapped too tightly since its wound-in tension cannot exceed the paper sheets' tensile strength.
In the paper web reeling process, the tension in the paper sheet of each successive layer tends to relieve the wound-in tension in the paper web beneath it. As the diameter of the wound paper roll increases, it has been determined that each successive web wrap on the roll should be wound with slightly less tension in order to minimize the reduction in the wound-in tension in the web layers beneath it.
Heretofore, in Pope-type reels, such control of the wound-in tension has been very difficult, if not impossible, to control since each new core, or reel spool, has been driven during the initial reeling stage, when the diameter of the wound paper roll is small, either by nipping contact with the support drum or by external contact with a nipped drive roll, such as a rubber covered tire, or both. In any event, the wound-in tension of the web on the new reel spool was provided essentially by the nipped frictional engagement of the reel spool against the support drum with the paper web in-between.
Therefore, during the period of time during the early states of the reeling process, when the newly formed wound paper roll is perhaps between about 5-15 cm in radial thickness, the wound-in tension is produced essentially by the frictional nipping engagement of the reel spool against the support drum. This is while the reel spool is supported by the primary arms over and against the upper periphery of the support drum. The wound-in tension produced this way is insufficient to prevent defects near the core, particularly when the wound paper rolls become large in diameter, such as about 250 cm or larger.
After the reel spool, with the initially wound layers of paper web on it, has been deposited on the guide rails in current Pope-type reels, a drive is connected to the reel spool to provide torque to drive the wound paper roll to provide the desired wound-in tension while the wound roll is held in nipping engagement with the driven support drum.
It has been determined that the three winding parameters influencing the desired hardness of wound paper rolls are 1) the linear nip pressure between the wound paper roll and the support drum; 2) the tension in the in-coming paper sheet; and 3) the torque applied to the reel spool/core of the paper roll being wound.
When nip pressure is the only wound web roll structuring technique utilized in producing the roll, there are limitations inherent in both the grades of paper which can be wound in this manner, and in the amount of nip pressure which can be effectively applied between the reel spool and support drum. For example, paper grades sensitive to nip pressure, such as creped and carbonless forms, cannot be wound at high nip pressures without adversely affecting the paper quality. Also, high nip pressures cannot effectively be applied to steel reel spools since steel spools do not possess sufficient compressibility, or ability to deform, to function properly in nipping engagement. Finally, low nip pressures alone will frequently not provide enough friction to drive the paper roll being wound.
Another limiting operational characteristic affecting the ability of current design Pope-type reels to wind a paper sheet effectively is that the range of tension in the in-coming paper sheet is limited to a relatively narrow range. Thus, while a greater sheet tension might be desired for the purposes of producing a more desirable roll structure, it might increase the frequency of sheet breaks and, therefore, not be feasible.
Another aspect of this design insures proper speed match between the spool and drum until the spool is brought into nipping contact with the drum. Conventional wind-ups use surface driving to accelerate the new spool to web speed. These drives lose contact with the spool prior to making nipping contact with the drum. An over-speeding or under-speeding spool causes web breaks during the web transfer.
Some mechanism have been designed to supply torque through the primary arm rotation in a Pope-type reel, such as shown and described in German document DE 40 07 329 A1. However, this apparatus is complicated, costly and might do more harm than good to the paper sheet being wound into a roll. Thus, in the German document apparatus, an expensive and complicated servo system positions the drive and reducer assembly relative to the winding core. The use of complicated sensors and hydraulic systems increase installation and maintenance costs. Failure of any component in the feedback loop could be hazardous to personnel, equipment and roll structure. Further, on conventional winding machines, the roll may require a 400 HP drive motor at one end of the reel spool. Over-hung weights approaching 12,000-13,000 pounds can be expected. This results in cross-machine nip pressure variants and spool deflection which cannot be avoided. In this regard, spool deflection alone can create sheet defects near the reel spool/core.